The present invention relates to an automatic document feeder (ADF) for use with an electrophotographic copier, digital copier or similar image recorder for selectively feeding ordinary documents in the form of separate sheets and a continuous document in the form of computer form (CF) paper.
An ADF is extensively used with the above-described kind of image recorder for automatically feeding a document to a glass platen of the image recorder while preventing it from jamming the path or from being damaged, then stopping it on the glass plate, and then discharging it after an image printed thereon has been scanned. Documents usable with the ADF include ordinary documents in the form of separate sheets and elongate documents such as CF paper. Generally, CF paper has a number of sprocket holes formed through a marginal area thereof. Specifically, the sprocket holes are positioned one after another in an intended direction of paper feed to mesh with the teeth of a sprocket which drives the CF paper. A sensor is located on the transport path of the CF paper to sense the sprocket holes, so that the transport of the paper may be controlled in response to the output of the sensor. An ADF having a capability for transporting such CF paper to the glass platen is disclosed in Japanese Patent Laid-open Publication No. 72455/1984. A drawback with a prior art ADF having such a capability is that the document transport control cannot be readily implemented for each of different kinds of documents. Moreover, it is difficult to accurately position a document in a predetermined position of a glass platen for imagewise exposure. Especially, sequentially locating consecutive pages provided on CF paper in the particular position on the platen is extremely difficult.